Square, the company famous for its tiny mobile credit-card reader, says that during the last week, the firm crossed a major benchmark: Businesses using Square’s various payment technologies processed $100 million in sales during a single shopping day.

Square’s record day caps a stormy year for the company founded by Jack Dorsey, the entrepreneur who also was an inventor of Twitter. Once considered among the most promising start-ups in the tech industry, Square, in 2014, was dogged by reports that it was bleeding cash and looking for a lifeline in the form of an acquirer. Its core business also came under threat, with Apple, Amazon, and PayPal pushing new payment initiatives.

But the year was marked by expansion beyond payments, too. Square acquired the food-delivery company Caviar; it created a financing business, Square Capital, which offers loans to businesses based on the business data that Square gleans from its customers’ payment record; and it partnered with Snapchat to let people transfer money through that messaging app.

I talked to Mr. Dorsey at the company’s San Francisco headquarters on Tuesday about Square’s past year, the company’s long-term prospects and the messy, unpredictable future of payments. Here is an edited transcript of our conversation.

Q.

Can you tell me what the $100 million-day means in terms of Square’s growth?

A.

It’s pretty significant. It signals that we’re still growing very fast. We’re still reaching out to the farthest ends of small businesses and independent sellers and the mobile folks.

Q.

It seems like your business got more competitive this year, with Apple, Amazon, PayPal others doing more on payments.

A.

It’s funny because five years ago we saw it as extremely competitive. Has it changed dramatically in the last year? Not in my viewpoint. There’s definitely more attention paid to it, and there’s definitely more options for buyers. We talk a lot about sellers, but we need to make sure they provide a great experience to their buyers.

It’s going to change. We have committed to making sure our sellers are empowered to make every sale. As we see more attention on NFC in this country, that will be more and more the case.

Q.

This has been a tumultuous year for Square, at least according to The Wall Street Journal. It reported potential acquisition talks and a $100 million loss in 2013. What’s your response to those reports?

A.

First and foremost, we have never been in any talks about an acquisition with anybody for our nearly six years as an idea and over five years as a company. That has never occurred. Second, we have never had any plans of any substance about an I.P.O. We’ve had no plans to engage the market and investors, no plans on when. We believe right now that being a private company is best for us.

“Loss” is an interesting word. You can consider it a straight loss, or you can invest in the company to grow the company so you can grow the network and the base of people using the service. We’ve chosen to spend money to grow the business.

Q.

But the larger narrative around Square is that your growth trajectory has changed. It doesn’t seem like the kind of fast-growing company it was a year or two years ago. Is that fair?

A.

I don’t think it’s fair. To be very frank, there were a lot of expectation on the company and I think we will meet and exceed those expectations, but our community of sellers, together, would rank as the 13th largest retailer in the United States.

Payments is always reported as a dirty, low-margin business. We invested in a lot of machine learning to minimize the risk and fraud potential. And our margins benefit from that, so the core payments business is extremely strong. At any point, we can decide that we want to have a profit from our payments business and slow down the growth of our business. That’s not the choice we’re making, because we want to grow into a global business.

Q.

Do you think the payments business is going to be the main part of Square’s business in the future?

A.

I think it’s important for every business to have a core you can depend on, and that is payments for us. That allows us to build experiences that we want to have, such as Caviar and Order. It also allows us to do something super-creative with the investment in machine-learning we made, flipping it on its head into Square Capital.

Square Capital allows us to take the deep understanding we have about our sellers and apply it in a way that allows them to grow their businesses. They can buy a new salon chair, they can move from a cart to a mobile truck or even to brick-and-mortar. That would just not be possible without a strong core business.

The payments business has a great margin because of what we’ve invested in reducing risk. But there are businesses [like Square Capital] built around data that have a higher margin, because it’s all software. So we are investing in those businesses to build up the core business.

Q.

I have no data for this, but I feel like it’s rare for me to go to a store outside of San Francisco that uses Square. I still go to many places that are in your target group that either don’t accept credit cards or have old-style card readers. Why is that the case?

A.

I think the data shows otherwise. One in four credit or debit cards in the United States have swiped through Square in 2014. That’s not just people who travel in New York or San Francisco.

Why do you see other terminals? Because there’s a lot of merchants locked into punitive contracts. These are long contracts, two years or three years. Ultimately, I think everyone wants something more cohesive, connected, that works as one system. And that’s what we provide. I think we are building an ecosystem of tools that connect together.

Q.

When do you think credit cards are going to go away?

A.

I guess my question is, does it have to happen? Why does it have to happen? Checks are still used today. I think our philosophy has always been it doesn’t matter what the payment device is, it’s just that the seller should be able to accept it.

Q.

That seems like a different vision than what you had a few years ago. It seems like paying with credit cards — paying with a physical item — was something you wanted to eliminate. It seemed you were building an elegant payment solution that was invisible. Is that going to happen?

A.

I think that is the manifestation of what we want, that we want to use everyday and everywhere. But I don’t think we can only build for that. We need to make sure that our sellers are set up to make every sale.